Apparatus and method for cleaning substrates/media disks

ABSTRACT

An apparatus and method for cleaning workpieces ( 5 ) using two pairs of substantially vertical rotating roller brushes ( 15 ) at each brush station whereby rotation of said brushes ( 15 ) propel workpieces ( 5 ) from one brush station to the next. Workpieces ( 5 ) are held for a predetermined period of time at each station by edgewheels ( 30, 31 ) which also rotate the workpieces ( 5 ). Cleaning fluid is sprayed onto workpieces ( 5 ) as they rotate to assist in removing particulate contamination. Method involves inserting a single workpiece ( 5 ) in between two pairs of rotating roller brushes ( 15 ) which scrub said workpiece as it is rotated by a pair of edgewheels ( 30, 31 ). There may be a divider shield ( 9 ) in between each brush station to prevent a large proportion of particulate matter and used cleaning fluid from traveling between the brush stations.

FIELD OF THE INVENTION

This invention relates to an apparatus and method for cleaningsubstrates and/or media disks by the use of rotating roller brushes.

BACKGROUND OF THE INVENTION

There are in the art a number of patent documents which describeworkpiece cleaners using roller brushes to scrub the workpieces. Oneexample is laid-open Japanese patent specification S61-8734 (Toshio etal) which describes a transfer member that can move a plurality ofworkpieces through cleaning stations with washing liquid sprayed ontothe workpieces. The workpieces are cleaned by a roller brush.

The workpieces, which are disc shaped with a central hole, is supportedat the central hole by the transfer member. This may cause a problem ofthe cleanliness of central hole being compromise by contact of thetransfer member.

Another prior art document, United States Patent No. 2007006406 (McEnteeet al) describes a horizontal scrubber type cleaning system. Theworkpieces are moved along stations of rotating brushes on a conveyorbelt. A well known problem with this system is the slippage which canoccur between conveyor belt and workpieces. Also, these types ofworkpiece cleaners require a complicated and often cumbersome linkagesystem to control movement of the member.

Another prior art example is U.S. Pat. No. 5,893,381 (Terui) which is ascrubbing method in a running liquid. This method requires theworkpieces to be moved along a bath of wash liquid on carriers. Thesecarriers are immersed in wash liquid and must be made to move theworkpieces in this state, thus necessitating specialized equipment inwhich to do so. Furthermore, the brushes are embedded in the scrubbingmeans and are difficult to replace.

Another example of a similarly disadvantaged invention is U.S. Pat. No.7,155,767 which uses a pair of annular plate scrubbers to clean theworkpiece by conveying the workpiece towards an opposite rotatingscrubber.

There is still a need for equipment with which to transport theworkpiece, and this is adds to cost as well as increases need formaintenance. Moreover, this invention does not allow for easymodification for a different sized workpiece.

Generally speaking, the cleaners of this kind requires in one form oranother for the workpieces to be transported around to where they areneeded. This usually involves cumbersome equipment that costs more andrequires higher maintenance.

It is therefore desirable to have a workpiece cleaner apparatus andmethod which can eliminate the need for the moving carrier or edgewheel,whilst maintaining flexibility and ease of modification to accommodatedifferent sizes of workpieces, as well as to reduce the risk ofsplashing of the cleaning fluid.

SUMMARY OF THE INVENTION

It is a primary object of the present invention to provide an apparatusand method for cleaning workpieces, especially those of a substantiallyflat disc shape such as magnetic hard disks used for storage ofinformation, substrates and media disks, etc.

It is another object of the present invention to provide a muchsimplified apparatus and method for cleaning workpieces by eliminatingthe need for complicated and cumbersome conveyance systems required totransport the workpieces along the cleaning process such as those thatappear in some of the above mentioned prior art.

It is yet a further object of the present invention to provide anapparatus and method for cleaning workpieces with an ability to changequickly and easily for different sized workpieces.

In accordance with the present invention, these objectives are achievedby provision of an apparatus for cleaning a workpiece comprising atleast one brush station, each brush station comprising: at least onepair of roller brushes, said roller brushes rotating in an mirror-likefashion with respect to each other and said roller brushes sufficientlyclose to one another such that when said workpiece is placed in betweensaid roller brushes, the workpiece is scrubbed on both sides by therotating roller brushes and said workpiece tending to move in a linearfashion in the direction of rotation of the roller brushes; and a pairof edgewheels able to move towards and away from each other, and saidedgewheels located such that when the edgewheels are at a positioncloser with respect to each other, the edgewheels hold the workpiece ina location so that the workpiece is scrubbed by the rotating rollerbrushes, and at least one of said edgewheels in rotation so as to causerotation of the workpiece at a predetermined rate, and when theedgewheels are at a position further with respect to each other theedgewheels allow the workpiece to move freely in between the edgewheels.

In one specific embodiment of the present invention, there are two pairsof roller brushes at each of the brush stations, said two pairs ofroller brushes in a substantially rectangular configuration andsufficiently close to each other such that when said workpiece is placedin between said roller brushes, the rotating roller brushes causing theworkpiece to move in the direction of rotation, and the said edgewheelwhen at the position closer with respect to each other holding theworkpiece in a location substantially central to the rectangle formed bythe two pairs of roller brushes. Also, the said roller brushes havetheir axis of rotation in a substantially vertical direction.

In another specific embodiment of the present invention, there are fourbrush stations located in parallel to each other and such that theroller brushes in each brush station rotates at a constant speed, andthe pair of edgewheels in each brush station move towards and apart fromeach other in a specific sequence so that a workpiece placed at a firstbrush station will be held there for a predetermined amount of time bythe pair of edgewheels located at the first brush station until it isreleased by the edgewheels and moved to a second brush station where itis held by the pair of edgewheels located at the second brush station,and in this manner the workpiece moves through all four brush stations.

It is also possible to have any number of brush stations arranged inparallel and configured so a workpiece will travel through all of thebrush stations after being held for a certain amount of time at eachbrush station by the edgewheel of that particular brush station.

The apparatus in one embodiment of the present invention comprises adivider shield in between each brush station, said divider shieldshaving a thin opening just enough for the workpiece to move through,thus preventing a large proportion of particulate matter and usedcleaning fluid from traveling between the brush stations. This dividershield may also reduce or prevent altogether any splash of the cleaningfluid that may occur.

According to the present invention, there is also provided a method forcleaning workpieces comprising:

-   -   a. placing a workpiece of a flat disc shape in between at least        one pair of roller brushes, said roller brushes rotating in a        mirror-like fashion with respect to each other and said roller        brushes positioned close enough to each other so as to scrub the        workpiece, and rotation of roller brushes causing the workpiece        to move in a linear fashion in the direction of rotation;    -   b. holding the workpiece in this location for a predetermined        amount of time by using a pair of edgewheels; and    -   c. moving the pair of edgewheels away from each other so that        the rotation of the roller brushes causes the workpiece to move        away from the roller brushes.

In a more specific embodiment of the present invention, the rollerbrushes have their axis of rotation in a substantially verticaldirection and there are two pairs of roller brushes arranged in asubstantially rectangular configuration.

Yet another embodiment of the present invention is a method of cleaninga workpiece using a plurality of brush stations comprising: inserting aworkpiece of a flat disc shape into a first brush station, said brushstation comprising: at least one pair of roller brushes, said rollerbrushes rotating in a mirror-like fashion with respect to each other andsaid roller brushes positioned close enough to each other so as to scrubthe workpiece, and rotation of roller brushes causing the workpiece tomove in a linear fashion in the direction of rotation; a pair ofedgewheels, said edgewheels able to move towards and away from eachother, and said edgewheels located such that when the edgewheels are ata position closer with respect to each other, the edgewheels hold theworkpiece in a location so that the workpiece is scrubbed by therotating roller brushes, and at least one of said edgewheels in rotationso as to cause rotation of the workpiece at a predetermined rate, andwhen the edgewheels are at a position further with respect to each otherthe edgewheels allow the workpiece to move freely in between theedgewheels; and moving the edgewheels away from each other so that theworkpiece is moved by the rotation of the roller brushes into a secondbrush station, wherein the roller brushes have their axis of rotation ina substantially vertical direction and there are two pairs of rollerbrushes arranged in a substantially rectangular configuration.

The rotation of the roller brushes and the edgewheels may be powered byone or more electric motors. A gear system may control the rotationalspeed of the roller brushes. Also, another gear and mechanical linkagesystem may control the rotational speed and position of the edgewheels.

In one embodiment of the present invention, there is one motor and beltsystem for each brush station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a front perspective overall view of an embodiment of thisinvention.

FIG. 2 shows a rear perspective overall view of an embodiment of thisinvention.

FIG. 3 shows a top overall view of an embodiment of this invention.

FIG. 4 a shows a front perspective overall view of an embodiment of thisinvention with the divider shields in place.

FIG. 4 b shows a front view of an embodiment of this invention with thedivider shields in place.

FIG. 5 shows a perspective view of the edgewheel mechanism in anembodiment of this invention.

FIG. 6 shows a side view of the edgewheel mechanism in an embodiment ofthis invention.

FIG. 7 shows a perspective view of a brush station in an embodiment ofthis invention.

FIG. 8 shows a top view of a brush station in an embodiment of thisinvention.

FIG. 9 shows a perspective view of a brush station with a workpieceinserted in between the roller brushes in an embodiment of thisinvention.

FIG. 10 shows a perspective view of a brush station with two of theroller brushes removed in an embodiment of this invention.

FIG. 11 shows a perspective view of a brush station with a three rollerbrush configuration in an embodiment of this invention.

FIG. 12 shows a top view of a brush station with a three roller brushconfiguration in an embodiment of this invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A workpiece cleaning apparatus according to one embodiment of thepresent invention will be described with reference to the drawings. FIG.1 shows a front perspective overall view of one of the embodiments ofthe present invention. FIG. 2 shows a rear perspective overall view,FIG. 3 shows a top overall view, FIG. 4 a shows a front perspectiveoverall view with the divider shields (9) in place, FIG. 4 b shows afront view with the divider shields (9) in place, FIG. 5 shows aperspective view of the edgewheel mechanism, FIG. 6 shows a side view ofthe edgewheel mechanism, FIG. 7 shows a perspective view of the brushstation, FIG. 8 shows a top view of the brush station, FIG. 9 shows aperspective view of the brush station with a workpiece (5) inserted inbetween the roller brushes (15), FIG. 10 shows the brush station withtwo of the four roller brushes (15) removed from the hollow shaft (85)within, FIG. 11 and FIG. 12 show a perspective and top view,respectively, of another embodiment of this invention whereby there areonly three roller brushes (15) to each brush station.

Referring to FIGS. 1, 2 and 3, the workpiece cleaning apparatus isconstituted of two rows of four brush stations (10, 11, 12, 13 and 16,17, 18, 19) in each row, each brush station (10) comprising two pairs ofroller brushes (15) and a pair of edgewheels, with an upper edgewheel(30, 33) and a lower edgewheel (31, 34). In each row, when the apparatusis switched on, the pair of roller brushes (15) rotate in a mirror-likefashion, that is to say, in an opposite direction to each other. Thepair of edgewheels (30, 31) can assume two positions: a first position,whereby the upper edgewheel (30) and lower edgewheel (31) are locatedcloser together, and a second position, whereby the upper edgewheel (30)and lower edgewheel (31) are located further apart. The brush stations(10, 11, 12, 13) are separated from dry parts such as electric motors,belting systems, mechanical linkages and gears, etc with a water proofdividing wall (70) and bellows (72) where the edgewheel members (36, 37)puncture the said dividing wall.

In the row of brush stations (10, 11, 12, 13) further from the dividingwall (70), the edgewheels (30, 31) are connected respectively to anupper edgewheel rod (36) and a lower edgewheel rod (37) at a preciselocation so as to be aligned with the workpiece (5) in between theroller brushes (15). Further down both edgewheel rods (36, 37) arelocated another pair of edgewheels (33, 34) that are aligned to the rowof brush stations (16, 17, 18, 19) closer to the dividing wall (70).

When a workpiece (5) is inserted into the first brush station (10) inbetween the two pairs of rotating roller brushes (15), it is immediatelypulled in by the rotation of the roller brushes (15). At this point intime the pair of edgewheels (30, 31) are in the first position, wherebythe upper edgewheel (30) and lower edgewheel (31) are located closertogether, and hence prevent the workpiece (5) from moving out the otherside of the roller brushes (15). The workpiece (5) is held at thislocation by the opposing forces caused by the rotation of the rollerbrushes (15) and the resistance provided by the pair of edgewheels (30,31). The edgewheels (30, 31) are also in rotation in the same directionso as to cause the workpiece (5) to rotate.

After a certain amount of time, the pair of edgewheels (30, 31) assumethe second position, whereby the upper edgewheel (30) and loweredgewheel (31) are located further apart. This allows the workpiece (5)to pass in between the pair of edgewheels (30, 31) and through to thesecond brush station (11). After this happens, the pair of edgewheels(30, 31) return to the first position, ready for another workpiece.

This process is repeated until the workpiece (5) exits the apparatusafter the fourth brush station (13) and gets collected and stored in anappropriate manner.

Referring to FIGS. 4 a and 4 b, there is a divider shield (9) betweeneach brush station, said divider shields having an opening for theworkpiece (5) to move through. The opening is provided with a curtain ofcleaning fluid which acts to prevent most of the particulate matter fromtraveling between the brush stations. This curtain of cleaning fluidalso rinses the workpiece (5) of impurities and particulates that may bepresent on the said workpiece.

There is also a means of applying a cleaning fluid (not shown) at eachbrush station (10, 11, 12, 13) to facilitate cleaning of the workpiece(5). Referring to FIG. 10, this cleaning fluid is applied by means of aplurality of fluid injectors (not shown) located above each roller brush(15) and spraying cleaning fluid into a central cavity formed by hollowshafts (85) located within each roller brush (15). The cleaning fluidwill then seep into the brushes by means of openings located along thehollow shafts (85). FIG. 10 shows the brush station with two of the fourroller brushes (15) removed from the hollow shafts (85) so that the saidopenings are visible.

The cleaning fluid can be any one of water or detergent or a combinationof these.

Referring to FIG. 5 and FIG. 6, it can be seen the mechanism thatcontrols the movement and rotation of the edgewheels (30, 31, 33, 34). Amotor (38) rotates a drive gear (41) which is in turn connected to afirst spur gear (42). This first spur gear is connected to a second spurgear (43). The first spur gear (42) drives a first screw (46). Thesecond spur gear (43) drives a second screw (47). The configuration ofthe gears is such that the first and second spur gears rotate in anopposite direction with respect to each other. This causes the first andsecond screws (46, 47) also to rotate in an opposite direction withrespect to each other. The first screw (46) is connected to a threadedsection of the upper edgewheel member (36), said upper edgewheel memberslidably fixed to a first guide rail (48) so that when the first screwis rotated, the upper edgewheel member (36) moves in an upwardsdirection. Similarly, the second screw (47) is connected to a threadedsection of the lower edgewheel member (37), said lower edgewheel memberslidably fixed to a second guide rail (49) so that when the second screwis rotated, the lower edgewheel member (37) moves in a downwardsdirection. This is the mechanism that provides for the pair ofedgewheels (30, 31) to move apart from each other. After a predeterminednumber of revolutions of the motor (38), the rotation is reversed so asto affect a reverse of this process, thus causing the pair of edgewheels(30, 31) to move towards each other.

Also in FIGS. 5 and 6 can be seen a drive gear (50) powered by a motor(not shown) and said drive gear (50) running a belt (51). When inmotion, this belt (51) rotates a pair of timing pulleys (52). Each ofthe timing pulleys (52) are connected to an edgewheel member (36, 37)such that rotation of the timing pulleys (52) causes rotation of theedgewheel members (36, 37). Idler pulleys (53) allow the edgewheelmembers (36, 37) to move towards and apart from each other withoutsubstantially changing the tension of the belt (51). This is themechanism which causes the workpiece (5) to rotate while in contact withthe edgewheels (30, 31).

FIGS. 5 and 6 also show the bellows (72) which prevent cleaning fluidfrom passing through.

FIGS. 7 and 8 show a brush station (10, 11, 12, 13) with the rollerbrushes (15) installed on the hollow shafts (85).

FIG. 9 shows a brush station (10, 11, 12, 13) with a workpiece (5) in atypical location where it is scrubbed by the roller brushes (15). Therotation of the roller brushes (15) tends to propel the workpiece (5)outwards, but the pair of edgewheels (30, 31) hold the workpiece (5) inplace.

FIG. 10 shows a brush station (10, 11, 12, 13) with two of the rollerbrushes (15) removed so that the hollow shafts (85) within are visible.The openings along the length of the hollow shaft (85) that can be seenin this drawing is for cleaning fluid to seep out to the roller brushes(15).

FIGS. 11 and 12 show a brush station with a different configuration ofroller brushes (15). There are three roller brushes (15) arranged in atriangle configuration. The workpiece (5) can be seen at a locationwhere it is to be scrubbed.

While the invention has been described with respect to specificembodiments, those skilled in the art will recognize that changes can bemade in form and detail without departing from the spirit and scope ofthe invention. For example, the brushes, edgewheels, bases and variousmechanisms may be constructed from any appropriate material. In lieu ofthe cleaning fluid, our invention can be used in conjunction withdifferent types of these cleaning fluids, including water. In lieu ofthe size of the roller brushes, any other size may be used with theproper modification of quantities such as, but not limited to, thedistance between the roller brushes and the position of the edgewheel.Accordingly, all such changes come within our invention.

1. An apparatus for cleaning a workpiece (5), said workpiece having asubstantially flat disc shape comprising at least one brush station (10,11, 12, 13), the at least one brush station comprising: at least onepair of roller brushes (15), said roller brushes rotating in an oppositedirection with respect to each other and said roller brushes (15)sufficiently close to one another such that when said workpiece (5) isplaced in between said roller brushes (15), the workpiece (5) isscrubbed on both sides by the rotating roller brushes (15) and africtional force between the rotating roller brushes (15) and workpiece(5) propelling said workpiece (5) in the direction of rotation of theroller brushes (15); a pair of edgewheels (30, 31) for holding theworkpiece (5) in place for a predetermined amount of time andsubsequently releasing the workpiece (5) to be propelled by the rotationof the roller brushes (15), said edgewheels (30, 31) are able to movetowards and away from each other, and said edgewheels (30, 31) locatedsuch that when the edgewheels (30, 31) are at a position closer withrespect to each other, the edgewheels (30, 31) hold the workpiece (5) ina location so that the workpiece is scrubbed by the rotating rollerbrushes (15), and when the edgewheels (30, 31) are at a position furtherwith respect to each other, the edgewheels (30, 31) allow the workpiece(5) to move freely in between the edgewheels (30, 31); and wherein atleast one of said edgewheels (30, 31) is in rotation so as to causerotation of the workpiece (5) at a predetermined rate.
 2. An apparatusfor cleaning a workpiece (5) according to claim 1 wherein there are twopairs of roller brushes (15) at each of the at least one brush station(10, 11, 12, 13), said two pairs of roller brushes in a substantiallyrectangular configuration and sufficiently close to each other such thatwhen said workpiece (5) is placed in between said roller brushes (15)and a frictional force between the rotating roller brushes (15) andworkpiece (5) propelling said workpiece (5) in the direction ofrotation, and said edgewheel (30, 31) when at the position closer withrespect to each other holding the workpiece (5) in a locationsubstantially central to a rectangle formed by the two pairs of rollerbrushes (15).
 3. An apparatus for cleaning a workpiece (5) according toclaim 1 wherein there are four brush stations (10, 11, 12, 13) locatedin parallel to each other and such that the roller brushes (15) in eachbrush station rotates at a predetermined speed, and the pair ofedgewheels (30, 31) in each brush station move towards and apart fromeach other in a specific sequence so that a workpiece (5) placed at afirst brush station (10) will be held there for a predetermined amountof time by the pair of edgewheels (30, 31) located at the first brushstation (10) until it is released by the edgewheels (30, 31) and movedto a second brush station (11) where it is held by the pair ofedgewheels located at the second brush station (11), and in this mannerthe workpiece (5) moves through all four brush stations (10, 11, 12,13).
 4. An apparatus for cleaning a workpiece (5) according to claim 3wherein there are a plurality of brush stations parallel to each other.5. An apparatus for cleaning a workpiece (5) according to claim 1further comprising a means of rotating the roller brushes (15).
 6. Anapparatus for cleaning a workpiece according to claim 5 wherein saidmeans of rotating the roller brushes (15) is at least one electricalmotor.
 7. An apparatus for cleaning a workpiece according to claim 6further comprising a power transmission system connecting the at leastone electrical motor to the roller brushes (15).
 8. An apparatus forcleaning a workpiece according to claim 7 wherein said powertransmission system comprises a belting system.
 9. An apparatus forcleaning a workpiece according to claim 7 wherein said powertransmission system comprises a gear system.
 10. An apparatus forcleaning a workpiece according to claim 1 further comprising a means ofmoving the pair of edgewheels (30, 31) toward and apart with respect toone another.
 11. An apparatus for cleaning a workpiece according toclaim 10 wherein the means of moving the pair of edgewheels (30, 31)toward and apart with respect to one another is at least one electricalmotor.
 12. An apparatus for cleaning a workpiece according to claim 11further comprising a power transmission system connecting the at leastone electrical motor to said edgewheels (30, 31), said powertransmission system is such that it causes the pair of edgewheels (30,31) in each brush station (10, 11, 12, 13) to move towards and apartfrom each other in a specific sequence so that a workpiece (5) placed ata brush station will be held there for a predetermined amount of time bythe pair of edgewheels (30, 31) located at the brush station until it isreleased by the edgewheels (30, 31) and moved to a next brush stationand the process is repeated.
 13. An apparatus for cleaning a workpieceaccording to claim 12 wherein said power transmission system comprises abelting system.
 14. An apparatus for cleaning a workpiece according toclaim 12 wherein said power transmission system comprises a gear system.15. An apparatus for cleaning a workpiece according to claim 1 whereineach brush station has an individual electric motor.
 16. An apparatusfor cleaning a workpiece according to claim 1 further comprising adivider shield (9) in between each brush station, said divider shields(9) having an opening for the workpiece to move through.
 17. Anapparatus for cleaning a workpiece according to claim 16 wherein theopening in the said divider shield (9) is covered by a curtain of fluid.18. An apparatus for cleaning a workpiece according to claim 17 whereinsaid curtain of fluid prevents most of any particulate matter frompassing through.
 19. An apparatus for cleaning a workpiece according toclaim 17 wherein said fluid is one of water, detergent, alkalinesolution, or a combination of these.
 20. An apparatus for cleaning aworkpiece according to claim 1 wherein each of the pairs of rollerbrushes are located close enough to each other so as to cause a desiredamount of scrubbing on the workpieces.
 21. An apparatus for cleaning aworkpiece (5), said workpiece having a substantially flat disc shapecomprising at least one brush station (10, 11, 12, 13), the at least onebrush station comprising: at least one pair of roller brushes (15), saidroller brushes rotating in an opposite direction with respect to eachother and said roller brushes (15) sufficiently close to one anothersuch that when said workpiece (5) is placed in between said rollerbrushes (15), the workpiece (5) is scrubbed on both sides by therotating roller brushes (15) and a frictional force between the rotatingroller brushes (15) and workpiece (5) propelling said workpiece (5) inthe direction of rotation of the roller brushes (15); a pair ofedgewheels (30, 31) for holding the workpiece (5) in place for apredetermined amount of time and subsequently releasing the workpiece(5) to be propelled by the rotation of the roller brushes (15), whereinsaid roller brushes (15) have their axis of rotation in a substantiallyvertical direction.
 22. An apparatus for cleaning a workpiece (5), saidworkpiece having a substantially flat disc shape comprising at least onebrush station (10, 11, 12, 13), the at least one brush stationcomprising: at least one pair of roller brushes (15), said rollerbrushes rotating in an opposite direction with respect to each other andsaid roller brushes (15) sufficiently close to one another such thatwhen said workpiece (5) is placed in between said roller brushes (15),the workpiece (5) is scrubbed on both sides by the rotating rollerbrushes (15) and a frictional force between the rotating roller brushes(15) and workpiece (5) propelling said workpiece (5) in the direction ofrotation of the roller brushes (15); a pair of edgewheels (30, 31) forholding the workpiece (5) in place for a predetermined amount of timeand subsequently releasing the workpiece (5) to be propelled by therotation of the roller brushes (15), and a means of rotating at leastone of the edgewheels (30, 31).
 23. An apparatus for cleaning aworkpiece according to claim 22 wherein said means of rotating at leastone of the edgewheels (30, 31) is at least one electrical motor.
 24. Anapparatus for cleaning a workpiece according to claim 23 furthercomprising a power transmission system connecting the at least oneelectrical motor to said at least one of the edgewheels (30, 31), saidgear system is such that it causes the at least one of the edgewheels(30, 31) to rotate at a predetermined rate.
 25. An apparatus forcleaning a workpiece according to claim 24 wherein said powertransmission system comprises a belting system.
 26. An apparatus forcleaning a workpiece according to claim 24 wherein said powertransmission system comprises a gear system.
 27. An apparatus forcleaning a workpiece according to claim 24 wherein both the edgewheels(30, 31) are caused to rotate in the same direction so as to cause theworkpiece (5) to rotate.